Amorphous semiconductor films, such as amorphous silicon films, are usually deposited on a substrate from a vapor phase, e.g., by decomposing raw gaseous material by glow discharge. Vapor phase deposition facilitates obtaining a film with a large surface area. Such amorphous semiconductor films have been utilized as photoelectric conversion films in low-cost photoelectric conversion modules. A polymer or metal film used as a flexible substrate facilitates obtaining a thin and light-weight photoelectric conversion module, and facilitates continuous growth of a photoelectric conversion film on an elongated substrate.
Japanese Patent Document No. H06-342924 discloses a module, as shown in FIG. 2, for efficiently generating electric power from an amorphous silicon photoelectric conversion film on a flexible substrate. The module includes a flexible polymer film substrate 1 and a plurality of columns of photoelectric conversion elements on the substrate. The photoelectric conversion elements are formed by dividing a photoelectric conversion film on the flexible substrate, a first electrode layer on the photoelectric conversion film and a second electrode layer between the substrate and the conversion film, into rows and columns. Third electrodes 2 are on the back surface of the substrate 1. A third electrode 2 is connected through holes in the substrate 1 to a transparent first electrode on one of two adjoining elements and to the second electrode between another one of the adjoining elements and the substrate. The third electrodes 2 are formed by dividing a metal electrode layer deposited on the back surface of the substrate 1, except the periphery thereof, into rows and columns.
To connect the columns of the photoelectric conversion elements, a connecting electrode, connected to the first electrode on an end of a column 20 of the connecting electrodes 2, is connected to another connecting electrode, connected to the second electrode on an end of an adjacent column 20 of the connecting electrodes 2. This connection is made by forming inter-column connecting portions 21 consisting of two connecting electrodes connected to each other.
A positive terminal 41 is led out from a positive electrode 31, i.e. a transparent first electrode on an end of one of the outermost columns 20 of the connecting electrodes. A negative terminal 42 is led out from a negative electrode 32, i.e. a second electrode on an end of another one of the outermost columns 20 of the connecting electrodes.
A plurality of the photoelectric conversion modules of FIG. 2 are connected in parallel with wiring 5 as shown in FIG. 3 to obtain an area sufficient to perform a desired photoelectric conversion. The methods for lead-out of the terminals and for parallel connection of the modules are disclosed in Japanese Patent Documents No. H07-22640 and H07-99336.
The photoelectric conversion modules of FIGS. 2 and 3 have the following disadvantages:
(1) For tight bonding of the metal film for the inter-column connecting portion 21, this film is made thin, e.g., of silver 1000 Angstroms thick. As a result, the inter-column connecting portion 21 has considerable electrical resistance. Since only half of the inter-column connecting portion 21 is utilized for photoelectric conversion, the other half is dead or inactive.
(2) Typically, laser patterning is used for dividing the photoelectric conversion film and the electrode layers into rows and columns. Even though the horizontal width of the module is greater than the vertical length, as shown in the figures, sufficient positional precision is still required in patterning longitudinal lines. This is difficult because the substrate tends to deform. Also, the time required for patterning is increased because of position control.
(3) The terminals 41 and 42 are often led out by soldering conductive tape, by bonding conductive tape with conductive adhesive, or by using conductive and adhesive tapes. Adhesives or adhesive tapes tend to exude from their proper locations.
(4) It is necessary to connect wiring 5, in addition to bonding the terminals 41 and 42 for parallel connection. As two kinds of conductors have to be dealt with, the connecting process is complicated, cost is increased, and yield is reduced.
(5) Since the wiring 5 is visible from the outside, the conventional flexible photoelectric conversion module has a poor appearance.